A Tri-State circuit element is constructed which is uniquely suited for use in large scale integrated circuit devices wherein a relatively large number of such Tri-State circuits are utilized to drive other circuitry contained within the integrated circuit device. One embodiment of a Tri-State circuit is constructed utilizing a single NAND gate (73), a single inverter (74), a single P channel transistor (76), and two N channel transistors (77, 78) yielding a circuit having a propagation delay of only two gate delays and requiring a total of only nine transistors. Another embodiment of this invention is a Tri-State circuit constructed utilizing a single NOR gate (84), a single inverter (83), a single N channel transistor (88), and two P channel transistors (86, 87). In this embodiment of my invention, a total of nine MOS transistors are required, and the propagation delay between the input terminal and the output terminal is equal to two gate delays.
An interface circuit for an information processing device comprises a plurality of buffer circuits each formed of a plurality of C-MOS tri-state buffers. The buffers are provided for communicating between the devices and an interface line which includes a power supply line and a signal line. Each buffer is powered from its specific power source and if this specific power source is inoperative, from the remaining power sources other than its specific power source.
A power switching circuit 12 for automatically switching between line-driven and battery power supplies 28 and 30 is disclosed. The power switching circuit selectively connects first and second input voltage terminals Vdd and Vbb to an output voltage terminal Vzz. When the line-driven power supply is on, a first transistor Q1 switches on to connect the first input voltage terminal to the output voltage terminal, and a second transistor Q2 switches off to isolate the battery. When the line-driven power supply is off, the first transistor switches off, and the second switches on to connect the battery powered second input voltage terminal to the output voltage terminal.
An output buffer circuit has a data input terminal which receives logic data, load and drive transistors, a driver for selectively turning on the transistors in accordance with the logic value of the logic data, a data output terminal which is connected to a power source terminal of the VDD level through a current path of the load transistor and is grounded through a current path of the drive transistor, and a capacitor connected as a load to the data output terminal. The output buffer circuit further has a transistion detector circuit for generating a pulse signal in response to a change in level of each of address signals, and a preset circuit for supplying, in response to the pulse signal, a charge or discharge current to the capacitor while a voltage at the data output terminal is not at the VDD/2 level.
A three state inverter driver is operated so that its output goes to a logic one briefly just prior to going to its high impedance state when commanded by a disable pulse. This characteristic is useful where a plurality of drivers are employed to operate a DRAM element.
A device is disclosed which combines the advantages of CMOS and bipolar using an existing parasitic bipolar device. As such high on-chip density is attainable with the device along with high speed capability while maintaining low power advantages.
